Turbine generators that exploit passive pressurized sources such as natural gas well heads have found utility in low power applications (100 watts or less). An example of such a generator is disclosed in U.S. Pat. No. 5,118,961 to Gamel and owned by S&W Holdings, Inc., the assignee of the present patent application. The reliability of these units has resulted in a wider variety of applications by relevant consumers, and attendant demands for higher power output.
A challenge with increased power output is the requirement for higher voltage levels. Devices that rely on the spatial separation of electrical connections to provide electrical isolation between the winding terminations may require a larger footprint to accomplish the required isolation. Units that service the petrochemical industry are often powered by high pressure hydrocarbon gases. Increased potential between electrical connections may result in arcing, creating an explosion hazard. Even where an explosion does not result, such arcing may lead to a build up of carbon deposits on the exposed connections that may eventually bridge between the connections, causing the unit to short out and incur structural damage.
One approach to increasing the power is to increase the size of the various components. Exemplary is U.S. Patent Application Publication No. 2005/0217259 by Turchetta, which discloses an in-line natural gas turbine that utilizes bevel gears to transmit the rotational power to a generator outside a pipeline. However, in spatially constrained areas (e.g. off shore drilling platforms), the footprint of such an approach may be prohibitive.
Increased power output generally requires a higher mass flow rate through a given unit, which leads to an increase in the amount of condensate that forms and accumulates in the unit. Existing units have been known to become flooded with accumulated condensation to the point of becoming inoperable.
Another issue in certain applications, independent of power level, is the effect of corrosive gases. Natural gas wells, for example, are known to contain hydrogen sulfide (H2S), also referred to as “sour gas.” The sour gas has a highly corrosive effect on metals commonly used in electric generators. Another common component indigenous to natural gas wells is water vapor, which is also corrosive and can cause operational problems when condensing out as a liquid.
Certain technologies utilize pressurized liquids to prevent hazardous gasses from entering unwanted portions of an assembly, such as disclosed in U.S. Pat. No. 5,334,004 to Lefevre et al. Where isolation from electrical machinery is desired, such an approach may require an isolation chamber distinct from the compartment housing the electrical machinery, as the use of liquids may be precluded for reasons of electrical isolation. The need for an isolation chamber will generally add to the required footprint of the generator.
What is needed is a gas turbine generator capable of utilizing a hydrocarbon medium without posing an explosion or carbon forming hazard, is resistive to the corrosive components that may be indigenous to the pressure source, and eliminates the potential of condensation flooding while maintaining a small footprint.